In recent years, methods for improving fuel efficiency by using resins in ducts in an engine room as automobile parts and thus reducing the weight have been widespread, and at the present time, polyamide materials are mainly used.
On the other hand, from the viewpoint of lower environmental burdens, a vehicle in which an exhaust gas recirculation mechanism is incorporated has also become popular. The exhaust gas recirculation mechanism returns the exhaust gas generated from the internal combustion engine to the intake duct for the purpose of suppressing the amount of NOx generated and also improving the fuel efficiency by reducing pumping losses. In this case, the inside of the intake duct is more exposed to acid than in a regular mechanism, and the environment of a high temperature and a high pressure is also created. The conventional resin ducts cannot sufficiently maintain the durability, causing the decrease in toughness, flexibility and strength. As a result, a problem of cracks and ruptures of ducts arises. Therefore, materials which are excellent in heat resistance, heat aging resistance, chemical resistance and toughness have been studied. Furthermore, in recent years particularly, as the space inside the engine room has been reduced, materials having flexibility in addition to heat resistance, heat aging resistance and chemical resistance have been required from the viewpoint of improving the assembling property, the vibration absorption and the like.
Since a polyphenylene sulfide (hereinafter abbreviated as PPS in some cases) resin has properties suitable for engineering plastics such as excellent heat resistance, chemical resistance, flame retardance, electric insulation, moist heat resistance and the like, the polyphenylene sulfide resin has been widely used for electric and electronic parts, communication device parts, automobile parts, and the like. On the other hand, since the PPS resin is hard and brittle, many studies have been reported in which the flexibility and the toughness are improved by blending an elastomer in the PPS resin. However, in many cases, only a certain degree of flexibility can be obtained because the blending amount of the elastomer is small. Therefore, there has been a limit to the expansion of the uses as a flexible material such as the use by bending the forming product freely. Furthermore, even if the blending amount of the elastomer is increased in order to impart high flexibility, properties resulting from the elastomer is exhibited strongly because a phase structure in which the elastomer phase forms a continuous phase while the polyphenylene sulfide phase forms a dispersed phase is formed. As a result, the excellent heat resistance and chemical resistance inherent to the PPS resin are sacrificed, and in addition, a new problem such as a remarkable decrease in mechanical properties after the heat treatment at a high temperature occurs.
In response to such problems, as a technique for improving the flexibility and the toughness of the PPS, for example, a composition composed of a polyphenylene sulfide resin having a certain melt viscosity and a certain extraction amount of chloroform and an olefin resin has been considered (for example, see Patent Document 1).
As a material which is excellent in toughness and chemical resistance, for example, a resin composition composed of a polyphenylene sulfide resin, a polyamide resin and an epoxy group-containing copolymer has been also considered (for example, see Patent Document 2).
Moreover, as a material which is excellent in toughness, impact resistance and chemical resistance, for example, a resin composition composed of a polyphenylene sulfide resin, a polyamide resin and an elastomer has been considered, wherein the polyphenylene sulfide resin forms a continuous phase while the polyamide resin forms a dispersed phase, and an acid-modified ethylene/a olefin copolymer elastomer is dispersed in the dispersed phase of the polyamide resin (for example, see Patent Document 3).
Furthermore, as a material for a blow hollow forming product which is excellent in mechanical strength and refrigerant impact resistance, for example, a resin composition composed of a polyarylene sulfide resin having a certain amount of carboxyl group and a certain melt viscosity and a polyolefin having an epoxy group, and a blow hollow forming product have been studied (see, for example, Patent Document 4).
In addition, as a material which is suitable for hollow forming products and is excellent in toughness, chemical resistance, and surface smoothness, for example, a resin composition composed of a polyphenylene sulfide resin and an elastomer of a polyamide resin and/or a saturated polyester resin has been considered (for example, see Patent Document 5).